In the Japanese Patent No. 5106019 publication (which will be referred to as the Patent document 1 described below), there is disclosed a cusp forming template. The template in this document includes or contains: a substantially semicircular cusp base forming part having, as a diameter, a sum of a nominal diameter (a diameter of a cylinder which forms an arcuate surface of a sizer block of which size is in agreement with both commissure parts of cut cusps) and a seam allowance; and a line drawing part comprising a coaptation zone forming part continuous to the cusp base forming part. Such a template is used to draw lines on a membrane to cut the membrane along those lines. Thus, cusp forming materials for cusp formation can be provided.